Rio Salado Oeste Final Environmental Impact Statement Salt River
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Los Angeles District South Pacific Division Rio Salado Oeste Final Environmental Impact Statement Salt River-Phoenix, Arizona Prepared by: U.S. Army Corps of Engineers, Los Angeles District Arizona Nevada Area Office 3636 North Central Avenue, Suite 740 Phoenix, AZ 85012-1936 September 2006 Proposed Action: Ecosystem restoration along an eight mile reach of the Salt River Type of Statement: Final Environmental Impact Statement (FEIS) Lead Agency: U.S. Army Corps of Engineers, Los Angeles District Cooperating Agency: City of Phoenix For Further Information: Scott K. Estergard U.S. Army Corps of Engineers, Los Angeles District Arizona-Nevada Area Office, Planning Section C 3636 N. Central Ave., Suite 900, Phoenix, AZ. 85012-1939 (602)640-2003, X-242, [email protected] Abstract: This final environmental impact statement (FEIS) analyzes the potential environmental impacts associated with the proposed Rio Salado Oeste project on the Salt River in Maricopa County, Arizona. The primary purpose of the proposed action is ecosystem restoration. The responsible federal lead agency is the Department of the Army, U.S. Army Corps of Engineers, Los Angeles District. The City of Phoenix is the non-federal sponsor. The study area for the project consists of an eight mile reach of the Salt River and adjacent lands in and near southwestern Phoenix, Maricopa County, Arizona. More specifically, the study area consists of the Salt River corridor from 19th Avenue downstream (west) to 83rd Avenue, between Lower Buckeye Road and Baseline Road. This study area is three miles wide and encompasses approximately 23.5 square miles. This document addresses the No-Action Alternative, the Recommended Plan, and four additional alternative plans developed to restore and improve native vegetation and wildlife habitat values in the project area. The recommended plan would entail earth moving, planting of vegetation and irrigation installation to facilitate restoration of 1,466 acres of riparian habitats along the Salt River. Restored habitats would consist of 170 acres of river channel (including 34 acres of in-channel wetland), 375 acres of cottonwood/willow forest, 417 acres of mesquite, 156 acres of other wetlands, 296 acres of riparian scrub and 52 acres of scrub shrub. Additional benefits would include recreational opportunities, general improvements in aesthetic quality, and a slight reduction in the potential for flood damage. Each alternative has been designed to minimize adverse impacts to the maximum extent practicable. The anticipated cumulative effects of implementation of the proposed action have been considered and addressed. Analyses and documentation are consistent with the National Environmental Policy Act (NEPA) and other applicable laws, regulations, and policies, and have been conducted in coordination with the City of Phoenix, the Gila River Indian Community, concerned resource agencies, and members of the public. Information referred to in this document, as well as in the accompanying feasibility report and appendices, is incorporated by reference. A 45-day comment period on the Rio Salado Oeste, Draft Environmental Impact Statement (EIS) began with the publication of the U.S. Environmental Protection Agency Notice of Availability in the Federal Register on May 12, 2006. A public hearing to discuss and receive comments on the Draft EIS was held at the Travis L Williams Family Services Community Center in Phoenix, Arizona on the evening of May 18, 2006. All comments received during the comment period were considered in the preparation of the Final EIS. Comments received during the public hearing or in writing, along with responses, may be found in Appendix E of the Final EIS. Unless otherwise requested, copies of the Final EIS will be provided on CD-ROM. Rio Salado Oeste September 2006 Final Environmental Impact Statement ES-1 EXECUTIVE SUMMARY ES. 1 INTRODUCTION This Final Environmental Impact Statement (FEIS) has been prepared by the U.S. Army Corps of Engineers (Corps), Los Angeles District, to analyze potential environmental impacts associated with the implementation of alternatives for the Rio Salado Oeste ecosystem restoration project. The study area is geographically located in the City of Phoenix, which lies within Maricopa County, Arizona. The study area is approximately eight miles long extending from 19th Avenue on the east downstream to 83rd Avenue on the west, and from Lower Buckeye Road on the north to Baseline Road on the south. The study area is approximately three miles wide and comprises approximately 23.5 square miles. While this is a large study area extending beyond the riverbanks, any implementation of project features would be associated with the river floodplain in an area referred to as the project implementation area. The project implementation area extends from 19th Avenue on the east to 83rd Avenue on the west, and is the area within the 100-year floodplain of the Salt River. The project implementation area averages two-thirds of a mile in width, and consists of approximately 3,315 acres. The study area lies between two other U.S. Army Corps of Engineers ecosystem restoration projects; Rio Salado Phoenix upstream and Tres Rios downstream. Information referred to in this FEIS, as well as in the accompanying Feasibility Report titled Rio Salado Oeste Interim Feasibility Report, Salt River – Phoenix, Arizona (hereafter variously referred to as main report, feasibility report and main feasibility report) and its appendices, is incorporated by reference. The FEIS provides a description of restoration alternatives and the No-Action Alternative; provides an analysis of the existing and future conditions of the area without the project, and; analyzes the impacts associated with five action alternatives that have been determined to be the most feasible. Alternative 5A has been identified as the recommended plan based on its achievement of project objectives and for its level of attainment of completeness, efficiency, effectiveness, and preliminary public acceptability criteria. ES.2 MAJOR CONCLUSIONS ES.2.1 FORMULATION AND SCREENING OF ALTERNATIVES The purpose of the proposed action is to restore degraded riparian ecosystem structure, function and dynamic processes to a more self-sustaining, diverse, and functional condition. Flood damage reduction was evaluated as an additional project purpose, but could not be economically justified. However, incidental flood damage reduction benefits would likely be obtained from an ecosystem restoration project. Potential additional benefits in the project area would include the following: passive recreation; improved water quality, air quality and aesthetics, and; noise reduction. Rio Salado Oeste September 2006 Final Environmental Impact Statement ES-1 Specific planning objectives reflect the problems and opportunities for desired positive changes along the Rio Salado Oeste reach of the Salt River. The established objectives were: to restore native riparian, wetland, and floodplain habitats and manage undesirable plant, fish, and wildlife species; to reduce flood damages to infrastructure and structures, and; to improve passive recreation and environmental-education opportunities. Alternative plans were developed during the feasibility study to meet the specified problems and opportunities and planning objective and constraints. The alternatives were then ranked based on completeness, effectiveness, efficiency, and acceptability and twelve were selected for further review. To narrow the array further, the study team determined the most significant criteria to use in comparing alternatives. These were: • Cottonwood/willow is an important and scarce cover type in Arizona and the Southwest. The study team, including the U.S. Fish and Wildlife Service (USFWS) and Arizona Game and Fish Department (AGFD), decided that cottonwood/willow cover type was the highest priority for restoration, followed by mesquite and wetlands. Due to the significance and scarcity of cottonwood/willow, alternatives not including this cover type were eliminated from further consideration. • Since the watershed is developed, tributaries to the river have been replaced by stormwater outfalls. These stormwater outfalls provide opportunities for restoration and for potential water harvesting. These outfalls also provide an inexpensive opportunity to direct additional water to the project area and associated restoration features. The stormwater measure is a necessary component of any alternative because of the restoration opportunities and potential water source. Therefore, alternatives not including that individual component were eliminated from further consideration. • Channel restoration is an important project component for various reasons. It provides a connection to other projects, is a potential means of water distribution, is important for the ecosystem, and contributes to reducing flooding potential. Therefore, alternatives not including that component were not considered. Applying these criteria to the array of alternatives narrowed the list to five alternatives, plus the No-action Alternative. The remaining five alternatives all include channel modification to maximize stormwater retention for habitat use. Alternative 4 includes active restoration of cottonwood and mesquite and emergent habitat, as well as active management to control invasives. Alternative 5 includes all of the above, plus the development of two existing gravel pits into lakes. Alternative 5A, the Recommended Plan,